Many satellites and other spacecraft, as well as some terrestrial stationary and vehicle applications, such as seagoing vessels, can include one or more energy storage flywheel systems to provide both a backup power source and to provide attitude control for the vehicle. In such systems, each flywheel system is controlled and regulated to balance the electrical demand in the vehicle electrical distribution system, and may also be controlled in response to programmed or remote attitude (or torque) commands received by a main controller in the vehicle.
Many energy storage flywheel systems include one or more components that are rotationally supported within a housing assembly. These components, which may be referred to as the rotating group, include, for example, an energy storage flywheel, a motor/generator, and a shaft. In particular, the energy storage flywheel and motor/generator may be mounted on the shaft, which may in turn be rotationally supported in the housing assembly via one or more bearing assemblies. In many instances, the shaft is rotationally supported using one or more primary bearing assemblies, and one or more secondary, or back-up, bearing assemblies. For example, in many satellite and spacecraft applications, the flywheel system may include one or more magnetic bearing assemblies that function as the primary bearing assemblies, and one or more mechanical bearing assemblies that function as the secondary bearing assemblies. Typically, the primary bearing assemblies are used to rotationally support the rotating group, while the secondary bearing assemblies are otherwise disengaged from the rotating group. If one or more of the primary bearing assemblies is deactivated due, for example, to a malfunction, or otherwise becomes inoperable to rotationally support the rotating group, the secondary bearing assemblies will then engage, and thereby rotationally support, the rotating group.
It is postulated that one or more of the above-mentioned components could become inoperable during energy storage flywheel system operation. In such instances, the entire energy storage flywheel system could become inoperable. Thus, it is desirable to provide sufficient redundancy within an energy storage flywheel system, most notably for space applications, to reduce the likelihood of system inoperability. Unfortunately, most redundancy schemes, such as dual motor/generators, and/or dual primary bearings, etc., can undesirably increase overall system weight.
Hence, there is a need for a redundant energy storage flywheel system for spacecraft applications that is fully redundant, yet does not significantly increase overall system and spacecraft weight. The present invention addresses at least this need.